The BASH shell will complain that a command cannot be found if the file with the given name does not exist in a directory listed in the $PATH environment variable.
You can see the current search path with
and add a directory to it with
I think setenforce lives in /usr/sbin/ which is on the root user's path by default but not on the path of regular users.
Another way around this would be to give the full path:
You can find out where setenforce is on your system using